In the spirit of Gödel's theorems, simulators are incomplete. Simulators exist because someone found a phenomenon or model interesting, and implemented a simulator for it. Thus, simulators are two steps away from reality. Or whatever you perceive as reality.
It is obvious that the T-bass drive is a method for changing frequency response of an open baffle system, as well as the dynamic behavior. Frequency response is easy to simulate. From my personal, subjective experience, the dynamics of living room music reproduction systems aren't accurately defined in models, let alone simulators. Maybe I'm just not up to snuff in the latest simulator news. Tell me.
It is also obvious that Graham Maynard's design is a little rough around the edges. So. We have a phenomenon, and no simulator. So that's a weakness in what? That's a weakness in the models and the simulators, not the device producing the effect.
How about you find a simulator that disproves the effect, sreten?
It is obvious that the T-bass drive is a method for changing frequency response of an open baffle system, as well as the dynamic behavior. Frequency response is easy to simulate. From my personal, subjective experience, the dynamics of living room music reproduction systems aren't accurately defined in models, let alone simulators. Maybe I'm just not up to snuff in the latest simulator news. Tell me.
It is also obvious that Graham Maynard's design is a little rough around the edges. So. We have a phenomenon, and no simulator. So that's a weakness in what? That's a weakness in the models and the simulators, not the device producing the effect.
How about you find a simulator that disproves the effect, sreten?
sreten said:Hi,
What is going on here ? Godels Theorem ? what has that got to with anything ?
Simulators are two steps away from reality ? and what reality is that ?
What phenomenon ? All I can see is a predictable passive circuit.
/sreten.
I wrote my last reply pretty carefully. If you read it again, you'll find the answers to your questions.
Thank you Kristleifur.
Sreten, there is nothing wrong with examining circuit activity, but the effect of the circuit needs to be heard to appreciate what is actually happening due to the T-bass interface between the amp loading and cone driving before anyone can decide what is or is not acceptable.
However to state this or that is wrong or correct based upon simulated steady sine amplitude/phase tells you little about about how it will sound when driving loudspeakers which are themselves dynamically impaired !
The circuit works best with low Z global NFB SS amplifier drive, and induces a dynamic first half cycle *current* boost which compensates for inadequate drivers dynamics in a manner which voltage drive cannot due to the manner in which voltage drive causes a driver to store energy, no matter how flatly the steady sine response has been EQed !
Cheers ....... Graham.
Sreten, there is nothing wrong with examining circuit activity, but the effect of the circuit needs to be heard to appreciate what is actually happening due to the T-bass interface between the amp loading and cone driving before anyone can decide what is or is not acceptable.
However to state this or that is wrong or correct based upon simulated steady sine amplitude/phase tells you little about about how it will sound when driving loudspeakers which are themselves dynamically impaired !
The circuit works best with low Z global NFB SS amplifier drive, and induces a dynamic first half cycle *current* boost which compensates for inadequate drivers dynamics in a manner which voltage drive cannot due to the manner in which voltage drive causes a driver to store energy, no matter how flatly the steady sine response has been EQed !
Cheers ....... Graham.
Hi,
I'm getting very bored, I have not stated anything.
Might as well now :
Steady state response and transient response are entirely interchangeable.
I'm not interested in handwaving "half cycle theory".
The voltage and impedance domain define the current domain.
Given two of the above the third is always defined.
You can look at the problem in any form you prefer.
I'm interested in what the circuit actually does. Voltage and impedance to
me are initially the most clear and the current cannot disagree with them.
That the circuit "operates" on some "current" principles not related
to the voltage and impedance transfer characteristics is not sensible.
They are the same thing.
/sreten.
I'm getting very bored, I have not stated anything.
Might as well now :
Steady state response and transient response are entirely interchangeable.
I'm not interested in handwaving "half cycle theory".
The voltage and impedance domain define the current domain.
Given two of the above the third is always defined.
You can look at the problem in any form you prefer.
I'm interested in what the circuit actually does. Voltage and impedance to
me are initially the most clear and the current cannot disagree with them.
That the circuit "operates" on some "current" principles not related
to the voltage and impedance transfer characteristics is not sensible.
They are the same thing.
/sreten.
Hi Sreten,
You write about 'bad engineering', and now "half cycle theory"; what are you on about ?
Surely you realise it is the first half cycle of LS cone motion which is the most distorted when a suddenly starting sine is applied to a loudspeaker ?
Even Linkwitz *illustrates* it on his website !
This distortion can be countered by equal but opposite increased first half cycle T-bass drive, but you are looking at the circuit in isolation using a dumb load as if that is sufficient !
You especially are one who makes posting anything here a nightmare, because all you do is snipe as if you know everything, and without actually CONTRIBUTING anything which is new !
To me you are not a learned Brit who can be respected !
Remember it is not theory, but the application of theory which counts !
Cheers ......... Graham.
You write about 'bad engineering', and now "half cycle theory"; what are you on about ?
Surely you realise it is the first half cycle of LS cone motion which is the most distorted when a suddenly starting sine is applied to a loudspeaker ?
Even Linkwitz *illustrates* it on his website !
This distortion can be countered by equal but opposite increased first half cycle T-bass drive, but you are looking at the circuit in isolation using a dumb load as if that is sufficient !
You especially are one who makes posting anything here a nightmare, because all you do is snipe as if you know everything, and without actually CONTRIBUTING anything which is new !
To me you are not a learned Brit who can be respected !
Remember it is not theory, but the application of theory which counts !
Cheers ......... Graham.
sreten said:
No !
Cone drive changes with voice coil current;
but current changes with composite driver impedance;
this impedance does not change with voltage;
so drive is not proportional to amplifier output voltage.
The T-bass compensates voice coil current for voltage modified driver impedance change during waveform time !
Hi CLS,
Apologies for delay in replying - 24 posts ago you asked about the influence of transformer inductance.
Yes this can have a significant effect, but might not be noticeable with drivers which do not reproduce efficiently at lower frequencies.
Before I wrote up on this I measured/tried different transformers, and even tried deliberately reducing inductance by parallelling up transformers.
Actually I found winding resistance introduced more significant loss than winding inductance, so if SS amps and the transformers I recommended are used then those should have high enough inductance for OB AF.
A 40-0-40Vac 500VA has more than enough inductance and driving capabilities - right down to sub-bass frequencies, and that is why I recommend same.
I'd love to fit T-bass driven free-air woofers to the rear shelf of my car, but it is too darned cold outside for me to be thinking about that at the moment.
Cheers .......... Graham.
kristleifur said:
Hi,
I generally answer posts addressed towards me.
Why don't you ask yourself your own question ?
From my perspective the answer is nothing much anymore.
I would suggest downloading TinaTi* and playing with the circuit.
/sreten.* http://focus.ti.com/docs/toolsw/folders/print/tina-ti.html
A lot easier to deal with than SPICE
I guess what Graham is trying to say is that a loudspeaker is NOT exactly the same thing as some (constant, "fixed" as well as linear) impedance. Specially if you consider the "first cycle" or otherwise non-repetitive transient behavior.
As someone else already pointed out, a simulation is only as good as the model(s) used to perform it.
Unless you have a really realistic model of a loudspeaker which takes into account all the non-linearities, transient effects, etc, SPICE is useless in this context. Unfortunately, AFAIK such a realistic model does not exist.